Fig. 5
From: Influence of the polar light cycle on seasonal dynamics of an Antarctic lake microbial community
Depth distribution of the major taxa in Ace Lake. Heat map depicting the relative abundance of the most abundant OTUs by depth (right-hand y-axis, U1 to L3), by season (left-hand y-axis: summer, red; winter, blue; spring, green) and by filter size (left-hand y-axis: 3, 0.8, and 0.1 μm). The relative abundances of OTUs in each of the 120 metagenomes are in Additional file 1: Dataset S1. OTUs are arranged by depth from the upper to lower zones (left-to-right x-axis). A group-average cluster based on the Bray-Curtis percent similarities between the square root-transformed OTU relative abundances has been overlaid (left-hand y-axis). The cluster analysis shows the extent to which overall OTU relative abundance is influenced by size fraction, season, and depth. The gradient bar shows the colour scale in percentage used for the relative abundance of the OTUs. Filter sizes: 3, 20–3 μm; 0.8, 3–0.8 μm; 0.1, 0.8–0.1 μm; Depths: U1, upper 1; U2, upper 2; U3, upper 3; I, interface; L1, lower 1; L2, lower 2; L3, lower 3 (see Additional file 2: Table S1 for specific information about sampled depths). The upper zone had high, peak relative abundance of Alphaproteobacteria (30%), Actinobacteria (20%), Chlorophyta (20%), Verrucomicrobia (16%), and Betaproteobacteria (15%), plus a variety of dsDNA viruses (36%), whereas the abundant members of the lower zone were Deltaproteobacteria (39%), Cloacimonetes (16%), Atribacteria (15%), Firmicutes (6%), Omnitrophica (5%), Euryarchaeota (5%), Chloroflexi (4%), Tenericutes (4%), and Acetothermia (3%). At the interface, Chlorobi (84%) and Deltaproteobacteria (39%) were abundant. Some taxa, such as Bacteroidetes (U, 37%; I, 18%; L, 13%), Planctomycetes (U, 10%; I, 6%; L, 4%), Parcubacteria (U, 9%; I, 7%; L, 11%), and Gammaproteobacteria (U, 29%; I, 4%; L, 3%) were represented throughout the lake. The major taxonomic groups were represented by specific genera or species; for example, Alphaproteobacteria consisted of Loktanella, Nisaea, Pelagibacter, and Yoonia (Additional file 1: Table S8)